CORKSCREW: The ‘corkscrew’ was an evasive manoeuvre used by bomber pilots to throw off nightfighters. Manoeuvres also existed to try and evade searchlight beams.

TINSEL: Beginning in December 1942 ‘Tinsel’ was one of the earliest forms of radio countermeasure fitted to bombers. It worked by broadcasting engine noise over the frequencies used for the ground control of nightfighters.

SPECIAL TINSEL: The TINSEL countermeasure could be inefficient because each bomber’s radio operator had to search for working Luftwaffe frequencies on his own. In June 1943 ‘Special Tinsel’ was introduced. RAF monitoring stations identified the Luftwaffe commentaries and then broadcast these frequencies to the bomber stream so that the entire raid could co-ordinate its jamming. However, like ‘Tinsel’ this was only effective against HF frequencies and could be routed around using VHF radio.

PHOTO: A wireless operator on a bomber tunes his set to the German HF fighter control frequencies, between 3 and 6 MHz. As soon as he's found a likely frequency he will switch on Tinsel to drown out the transmission. As Tinsel relied on the manual efforts of many wireless operators, not all of whom would find the correct frequency, it was somewhat inefficient. So in 1943 Bomber Command introduced 'Special Tinsel', whereby monitoring stations in England hunted down the Luftwaffe's broadcast commentary and then broadcast the wavelength to all the bombers so that the mass of bombers in the stream could spot-jam the frequency.

AIRBORNE CIGAR: With the Germans increasingly using VHF to communicate between the ground and air, demands for an airborne VHF jammer grew. ‘Airborne Cigar’ (often referred to as ABC) added a German-speaking operator to specially equipped bombers that would fly at intervals within the bomber stream, hunting out frequencies to jam.

MANDREL: One of the primary RAF radar jammers, a line or ‘screen’ of Mandrel aircraft would jam early warning radars on the approaches of the raid.

ILLUSTRATION: Short Stirling 'L' for 'Love', No. 199 Squadron, flew Mandrel patrols in support of the bombing campaign. Mandrel, like most barrage jamming systems, was most effective when the radar was pointed in the direction of the jammer, so the RAF set up Mandrel patrols on the approaches to raids and down the axes that the raids would withdraw.

PIPERACK: American variants of Mandrel, with the call signs Dinah II and Piperack, would accompany raids, spot-jamming a variety of radars.

CORONA CONTROLLERS: In October 1943 the RAF began to use German-speaking operatives (many of them Jewish refugees from Germany) to pose as Luftwaffe fighter controllers. Their successes were limited (though on the first occasion they drove the German controller into a fit of apoplexy). Occasional fog warnings broadcast over the airwaves could cause some nightfighters to divert or land early.

CORONA JAMMING: While the RAF ‘Corona’ operatives gummed up the airwaves with fake radio checks, the Germans tried various methods to counter the programme such as using women controllers. The RAF then deployed woman operatives of their own and the result devolved into the world’s first electronic ‘flame war’ with both groups openly insulting each other across the airwaves. Eventually, ‘Corona’ became a jamming system, playing records of Hitler speeches over the fighter control frequencies so as to garble any attempts to use the airwaves.

HIGH-RATE WINDOW: Window was the codename for tinfoil strips, used to fill German radar screens with clutter. In the period covered by the game it is assumed that Window is universally being deployed to protect raids, but this card represents an especially dense deployment of Window. Until the summer of 1944 the German long-wavelength SN-2 radar was completely immune to Window.

DARTBOARD: See the German entry on ANNEMARIE. The British countermeasure to this was ‘Dartboard’, which used the BBC transmitter at Crowborough, the most powerful station in Europe, to block ‘Annemarie’. ‘Dartboard’ began broadcasting in December 1943.

PHOTO: A cloud of Window (the spray of sparkles to the right of the picture) is released into the bomber stream. Initially the Window bundles were quite large, with 2,000 strips making up a package of about 27 ounces. As each bomber popped out a bundle at the rate of one a minute, this meant vast quantities of aluminium foil were used. Fortunately, American industrial know-how came to the rescue, with the development of a rotary cutter that that sliced the foil and bent it into a 'V' shape for rigidity. Seventy-five of these cutters were flown to Britain as priority cargo. The strips they produced were thinner and more efficient than the original Window. Type 'C' Window made an 800-strip bundle of 6 ounces, while the cellophane-backed Type 'E' Window reduced the weight to a manageable 2.6 ounces.